http://ldd.lego.com/
With the free Digital Designer software you can build absolutely anything with virtual LEGO bricks right on your computer. Then you can buy the real bricks to build your creation and you can share it with thousand of other LEGO fans.
One of the problems I used to face every time I wanted to make my own lego models was that I never had enough bricks of the kind I was needing. It must be one of those “Murphy´s laws” that the brick you just need is the one you lack!
Until now, there was a partial solution to this issue: the L-cad program allowed you to design your model in the computer so that you could afterwards order the pieces you wanted. This walkaround was (is) very useful, but if there were an easier option to custom design-custom order models which was backed by lego, that would be amazing, and if it were user friendly… whoa!
Well, so a big WHOA! to lego, since they have done exactly that. Besides giving the users an easy way to design models on the computer, they have made it just as easy to order those models as custom sets. Again, WHOA!! 😀